dbt-postgres 'microbatch' strategy

[MichelleArk]

resolves #149
docs dbt-labs/docs.getdbt.com/#

Problem

As part of dbt-labs/dbt-core#10624, dbt-postgres needs to implement a default microbatch strategy.

Solution

Although it is not write-optimized for partitioned data, we will use merge under-the-hood in dbt-postgres for now, as dbt-postgres does not yet support partitioning.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-postgres contributing guide.

[mikealfare]

Approval conditional on repointing to main of course.

[MichelleArk]

Confirmed the failing tests are expected on tests/functional/adapter/test_incremental_microbatch.py::TestPostgresMicrobatch::test_run_with_event_time. Going to go ahead and merge on failing CI here as this will just be intermittent until dbt-labs/dbt-core#10624 is merged.